The present application is the U.S. national phase under 35 U.S.C. xc2xa7371 of International Application No. PCT/JP00/02359 filed Apr. 12, 2000.
The present invention relates to a rain-water storing permeation structure, and a water storing block and a water-storing block connecting member that are used for such a structure, and more specifically concerns a rain-water storing permeation structure which can be applied to facilities, such as architectures like buildings, roads, water channels, parks and play grounds, factory sites and domestic sites, as well as water storing blocks used for such a structure and a connecting member for connecting the water-storing blocks to each other.
Conventionally, most of rain water permeated the soil, or formed ground water. Rain fall was held in the soil as a whole in various states, and exerted the following functions: It served as a water supply source required for growth of trees and other plants, adjusted the temperature of the earth surface through evaporation from the surface of the soil when it was hot, and also adjusted the amount of water of rivers.
However, in recent years, buildings, paved roads, etc., have increased due to rapid land developments and pavements of roads, resulting in less land where the soil is directly exposed to the surface in roads, play grounds and factory sites. For this reason, rain water is allowed to flow sewage systems and rivers through drainage channels, without penetrating the soil, thereby causing the following problems:
(1) Reduction and exhaustion in ground water, and the subsequent land subsidence.
(2) Occurrence of a heat island phenomenon due to inability of heat removal from the earth surface because of less water evaporation and the subsequent less heat absorption by vaporization.
(3) Concentration of rain water into sewage systems and rivers at the time of a heavy rain, and the subsequent occurrence of deluge and flood, or necessity of works for river control systems, and for expansion of sewage systems, etc. in an attempt to prevent such disasters.
In order to solve these problems, a method has been proposed in which: the ground is excavated to form a hole, a rain-water storing permeation structure is installed therein, and parks, roads, etc. are formed thereon, or buildings are built thereon. As described below, two types of such a rain-water storing permeation structure have been known:
(a) A structure based upon a concrete unit engineering method (Nikkei Construction, published on Mar. 13, 1998) in which a tank made of reinforced concrete is constructed as water-shielding material layers, and concrete blocks each of which has a void at a ratio of approximately 80% and also has each side set as large as 1.2 m are stacked and housed in this tank, and after a lid layer has been placed, a soil layer is further formed thereon so as to form a park, etc.
(b) A center-to-center* block engineering method (disclosed in a catalog of Hayashi Bussan K.K.) in which: a tank is formed by using a water-proof sheet as a water-shielding material layer, and in this tank, water-storing layers are formed by stacking and housing cage-shaped hollow blocks made from polypropylene, each of which has a trapezoidal pyramid shape measuring 360 mmxc3x97360 mm in upper surface, 270 mmxc3x97270 mm in bottom face, and 260 mm in height, with a void at a ratio of approximately 95%, and after a lid layer has been formed thereon, a soil layer is further placed thereon.
However, in the case of the concrete unit engineering method, since the weight of the concrete blocks is very high, its base portion needs to be formed by a high-strength material such as reinforced concrete, and a long construction period is required. Consequently, the construction costs become high as a whole.
Moreover, upon construction of the water-storing layers, a heavy machine is required in assembling the heavy concrete blocks. When such a heavy machine is used, a large working space is required, with the result that the land having a limited area cannot be used to an extent of 100%, thereby limiting the rain-water storing capability.
In the case of the center-to-center* block engineering method, the cage-shaped hollow blocks made of polypropylene (PP) do not have a sufficient compression strength; therefore, as is also described in the catalog, PP blocks can not be stacked with a depth of the water-storing layers exceeding 3 m. This limits the rain water storing capability per construction area. Moreover, PP is not sufficiently resistant to degradation due to microorganisms, etc., in the soil.
The objective of the present invention is to provide a rain-water storing permeation structure which is easily constructed without the need for a heavy machine, has a superior load-resistant property, and provides a sufficient depth and the subsequent great rain-water storing capacity, as well as water storing blocks used therein and a connecting member for connecting these water-storing blocks.
In order to achieve the above-mentioned objective, the rain-water storing permeation structure of the present invention features a construction which is provided with a water-shielding layer placed in a recessed section in the ground, a water-storing layer that is constituted by water-storing blocks made of a hard resin foam member having an inner space, and that is placed inside the water-shielding layer, and a lid layer.
The water-storing block made of a hard resin foam member having an inner space has a high compression strength and a superior load resistant property, and is light weight and easily manufactured at low costs. Therefore, it is possible to provide a deep construction of the water-storing layers, and since no heavy machine is required, it is possible to reduce the working space; thus, it becomes possible to provide a rain-water storing permeation structure having a high rain-water storing capacity per construction area. In particular, its superior load resistant property enables the upper surface to be used as roads, and the coverage of such a wide area makes it possible to store and utilize a large amount of rain water, and consequently to reduce damage from heavy rain fall.
The water-storing layer is formed by the water-storing blocks that are arranged, stacked and placed therein; thus, a number of small voids for storing rain water are formed. The percentage of void of the water-storing block is set to not more than 70%, and more preferably, in the range of 40 to 65%. The percentage less than 40% causes a reduction in the rain-water storing capacity, and the percentage exceeding 70% tends to cause an insufficient compression strength with respect to the load applied from above.
The upper surface of the rain-water storing permeation structure of the present invention can be utilized as sites for buildings, roads, play grounds, parks, gardens, etc. Therefore, with respect to the surface layer, layers, such as concrete bases, paved road surfaces, lawns, tartan tracks, soil, etc. are formed. The level of the upper surface of the lid layer is determined by taking into consideration the purpose of use, peripheral conditions, etc., and in general, it is set to virtually the same level as the peripheral soil layer, with the surface layer being included.
The water-shielding layer, which has a function to prevent stored rain water from leaking and flowing away, is made from a material having no water permeability. In general, a soil layer surrounds the rain-water storing permeation structure; however, not limited by this, structures such as concrete walls and concrete fences may surround the rain-water storing permeation structure.
The lid layer of the rain-water storing permeation structure of the present invention is preferably designed so as to include a water permeable material layer.
The lid layer has the following functions: prevention of soil from flowing into the inner voids of the water-storing block housed inside the water-storing layer; formation of a soil layer as the surface layer for effectively utilizing land; and prevention of stress from being concentrated on the water-storing block that tends to be adversely effected by a local load. On the top of the water-storing blocks, concrete floor plates, tiles, steel plates, natural stone plates, etc., are placed as the lid layer, and a soil layer is placed thereon as the surface layer, if necessary. A road may be formed as the surface layer.
In the case when the lid layer having no water permeability is placed as described above, a separate water-collecting facility such as a water-collecting ditch needs to be placed so as to introduce rain water into the rain-water storing permeation structure.
The application of a water-permeable material to the lid layer makes it possible to directly introduce rain water over the rain-water storing permeation structure into the rain-water storing permeation structure; thus, it is possible to greatly reduce water-collecting facilities to be attached to the rain-water storing permeation structure especially when it covers a wide area. In this arrangement, even in the event of a heavy rain, no soil forming the soil layer on the rain-water storing permeation structure is carried by water into a rain-water collecting facility and lost, which is advantageous. Moreover, when the road surface is heated, stored rain water is allowed to evaporate through the water-permeable lid, thereby cooling the road surface. Thus, it is possible to effectively reduce the heat island phenomenon.
It is preferable to place soil, water-permeable concrete floor plates, a sheet or blocks formed by binding particle-shaped or fiber rubber chips having a water-permeable property by using a binder, etc. on the water-permeable lid layer as the surface layer. In the case of a soil layer, it is more preferable to form a layer structure in which a coarse crushed stone layer, a ballast layer and a surface soil layer stacked from below with the higher layer having a finer grain size.
Moreover, the water-storing block of the present invention features a structure which has an external wall having a polygonal column shape with an inside void capable of storing water, is made of a hard resin foam member that can be buried in the soil, and also has an external wall face support section for receiving a pressure imposed on one face of the external wall having the polygonal column shape, and a diagonal support section connecting to the external wall face support section, for dispersing the pressure imposed on the face.
In the above-mentioned structure, even when it is buried deep in the soil and subjected to a strong soil pressure imposed sideways on the water-storing block, the external wall face support section, which receives the pressure imposed on one surface of the external wall having the polygonal column shape, first exerts a strong resistance, and upon receipt of a greater soil pressure, the diagonal support section connecting to the external wall face support section effectively disperses and weakens the soil pressure; thus, the side wall of the block becomes less susceptible to distortion and the resulting damage and destruction. Therefore, it is not necessary to take it into consideration to slant the pit walls so as to make it wider on the surface side in its cross-section and to assemble the blocks along its normal face; thus, it becomes possible to increase the water-storing capacity. Moreover, since the block is made of a hard resin foam member, it is light and no problem is raised in the strength even when a multi-stage layered structure is provided. It is also possible to easily construct without increasing construction costs. As a result, the advantages of the hard polystyrene foam blocks are sufficiently maintained, and it becomes possible to provide blocks capable of achieving a water-storing capability with a large capacity.
In the water-storing blocks of the present invention, the void of the water-storing block is preferably constituted by a void separated into a plurality of sections, and it is preferable that the void is surrounded by at least the diagonal support sections.
With this arrangement, more wall sections surrounding the void are formed so that a strong resistance is exerted against the soil pressure imposed from above, and so that the soil pressure, imposed sideways, is effectively dispersed by the wall sections surrounding the void surrounded by the diagonal support sections.
It is preferable to design the external wall of the water-storing block of the present invention to have an octagonal column shape formed by chamfering four corners of a virtually square column in an up and down direction, with each of the edge portions of the side having a circular arc shape protruding outward.
With this arrangement, the sides except the chamfered corners are made to contact each other so that a number of blocks are two-dimensionally placed in a stable manner, and since a void is formed between the corners, the percentage of void is increased and the amount of water storing is increased. Moreover, since the end portions of each side are formed into a circular arc shape protruding outward, it is possible to avoid concentration of stress at the end portions of each side, and consequently to increase the durability.
In the water-storing block of the present invention, it is preferable to form the corners of the inner walls of the void into an circular arc shape.
This arrangement makes it possible to disperse a stress on the corners at which concentration of stresses tends to occur, and consequently to ensure a higher durability.
The hard resin foam member of the water-storing block of the present invention is preferably made of styrene foam having an expansion ratio of at least not less than 20 times.
This arrangement makes it possible to achieve light weight and a reduction in the material costs, and an easy lamination process is achieved so that even in a pit deeply formed in the ground, a multi-stage laminated layers are formed, thereby making it possible to increase the water-storing capacity.
Moreover, the water-storing block connecting member of the present invention features that a plurality of claws, made of resin, for sticking the water-storing blocks respectively, are formed on the connecting member main body in a dispersed manner around the axis thereof, and a housing space for another member is formed between the adjacent claws in the circumferential direction around the axis. Here, the size of housing space for another member is set to a size in which a predetermined number of the claws are inserted in a manner aligned in the circumferential direction around the axis.
This arrangement provides the following functions [a] through [c]:
[a] For example, in an EUP engineering method (underground water-storing engineering method) in which a plurality of empty water-storing blocks are connected so as to form a civil engineering structure capable of drawing water, etc. stored inside the respective water-storing blocks, even in the case when the respective water-storing blocks are connected by the water-storing block connecting members, since the claws and the connecting member main body are made of resin, they do not cause rust, thereby making it possible to improve the durability.
[b] Moreover, as described above, the housing space for another member is formed between the adjacent claws in the circumferential direction of the axis, and the size of the housing space for another member is set to a size in which a predetermined number of the claws are inserted in a manner aligned in the circumferential direction around the axis. Therefore, when a plurality of water-storing block connecting members (hereinafter, xe2x80x9cwater-storing block connecting memberxe2x80x9d is occasionally referred to simply as xe2x80x9cconnecting memberxe2x80x9d) are packaged, the respective connecting members 2 can be packaged in an overlapped manner in the following sequence, for example, as illustrated in FIGS. 14 to 16 (in FIG. 14, with respect to the connecting members 2, a connecting member on the uppermost side of the Figure in an up and down direction is referred to as the first connecting member, followed by the second connecting member, the third connecting member, the fourth connecting member, the fifth connecting member and the sixth connecting member in succession downward in the Figure).
{circle around (1)} The respective claws 3 of the second connecting member 2 are placed adjacent to the respective claws 3 of the first connecting member 2 in the circumferential direction around the axis, when viewed in the axis direction of the connecting member main body 4 of the first connecting member 2; in this manner, the respective connecting member main bodies 4 are superposed on each other.
{circle around (2)} The respective claws 3 of the third connecting member 2 are placed adjacent to the respective claws 3 of the second connecting member 2 in the circumferential direction around the axis, when viewed in the axis direction of the first (and second) connecting member 2; in this manner, the respective connecting member main bodies 4 are superposed on each other.
{circle around (3)} In this manner, one connecting member 2 is superposed on another connecting member 2 in succession.
{circle around (4)} When a predetermined number of claws 3 of the connecting member 2 have been inserted between the respective claws 3 of the first connecting member 2, when viewed from the axis direction of the first connecting member 2, etc., the above-mentioned processes {circle around (1)} through {circle around (3)} are repeated based upon, for example, the connecting member 2 that was superposed lastly.
In other words, the respective claws 3 of the next connecting member 2 are placed adjacent to the respective claws 3 of the connecting member 2 in the circumferential direction around the axis, when viewed in the axis direction of the connecting member 2 that was last superposed; in this manner, the respective connecting member main bodies 4 are superposed on each other.
The claws 3 are normally formed with a narrowed top portion when viewed in the radial direction of the connecting member main body 4, and with this narrowed top shape, the respective claws 3 of the connecting member 2 to be superposed are allowed to enter a space between the claw 3 of the adjacent connecting member 2 in the superposing direction and the claw 3 adjacent to this connecting member 2 in the claw width direction; thus, it is possible to avoid an increase in the distance between the connecting member main bodies 4 of the two connecting members 2 due to interference between the claws 3 of the connecting members 2 adjacent to each other in the superposing direction.
{circle around (5)} By repeating the above-mentioned processes {circle around (1)} to {circle around (4)}, a plurality of connecting members 2 are superposed on one another.
[c] By superposing them in the manner as described in [b] above, the distance between the connecting member main bodies of the adjacent connecting members in the height direction of the claws is set to be shorter than the height dimension of the claws.
Therefore, it becomes possible to extend the service life of the water-storing block connecting member, and also to package a plurality of water-storing block connecting members in a compact manner.
In the present invention, the following arrangement is preferably made: the connecting member main body of the water-storing block connecting member is formed into an annular shape with the claws being placed on the peripheral edge of the connecting member main body; a plurality of assisting claws, made of resin, for sticking the water-storing blocks respectively, are placed on the inner circumferential edge of the connecting member main body, in a manner so as to have the same positional phase as the above-mentioned claws around the axis; the claw width of the assisting claw is set in such a manner that, when viewed from the axis direction, the assisting claw is positioned between a first hypothetical radial line extending from the axis to one edge end in the width direction of the claw and a second hypothetical radial line extending from the axis to the other edge end in the width direction of the claw; a housing space for another assisting member is formed between the adjacent assisting claws in the circumferential direction of the axis; and the size of the housing space for another assisting member is set to a size that allows a predetermined number of the assisting claws to enter in the circumferential direction of the axis in an aligned state.
In the above-mentioned arrangement, the claw width and the layout of the assisting claws are set as described above and the housing space for another assisting member is formed between the adjacent assisting claws in the circumferential direction of the axis; therefore, in the case when the connecting member main bodies of the respective connecting members are superposed in the sequence as described in [b], the assisting claws are placed adjacent to each other in the same manner as the claws so that it becomes possible to avoid problems such as incapability of the superposing process due to interference between the assisting claws.
Moreover, the assisting claws are placed on the inner circumferential edge of the annular connecting member main body in such a manner that, in the state where a force is applied so as to allow the claws and the assisting claws to stick the water-storing blocks made of resin, it is possible to prevent the center portion of the connecting member main body from deflecting toward the water-storing block, and also to prevent the claws from tilting outward due to this deflection and sticking the water-storing blocks in this state. Therefore, it becomes possible to further increase the connecting force.
Each of the claws and the assisting claws of the water-storing block connecting member of the present invention may be formed into a double-claw type so that, with the respective centers in the length direction of the claws and the assisting claws being located in between, the first claw portion on one side and the second claw portion on the other side are allowed to stick respective water-storing blocks adjacent to each other in the layer stacking direction.
With this arrangement, it is possible to connect a plurality of water-storing blocks in an abutting manner by using one connecting member, and also to connect the adjacent water-storing blocks in the layer stacking direction.
Therefore, it is possible to reduce the number of the connecting members per civil engineering structure, and also to reduce costs required for the construction work.